Electrohydraulic Control for Farm Vehicles

When standard equipment proved to be too heavy and underpowered for spraying operations in fields laden with heavy clay and gumbo-like soil, Bossuyt Brothers Farms designed a unique, lightweight solution using standard, off-the-shelf components and an electrohydraulic controller. The resulting hydraulic four-wheel-drive assist system provides consistent operation of the front wheels even in highly dynamic, high torque conditions.

"The OEM equipment is just too heavy and underpowered to operate effectively in our fields," Corey Bossuyt said in an interview. "We needed something a lot lighter with a better power-to-weight ratio and, as it turned out, the only way to get it was to build it ourselves."

Bossuyt Farms has experience with truck frame sprayers that essentially utilize a standard pickup truck for the engine, powertrain, and cab. These systems were light enough to maneuver in the fields, but only provided rear-wheel-drive operation, and not the four-wheel drive needed for wet field conditions.

A hydraulic four-wheel-drive assist system provides consistent operation of the front wheels for a spraying vehicle developed by Bossuyt Brothers Farms. This unique, lightweight solution uses an electrohydraulic controller and standard, off-the-shelf components to increase the productivity of spraying operations in fields laden with heavy clay and gumbo-type soil.

"There simply is no practical way to get mechanical power to the front wheels because they're mounted on long drop steering spindles to achieve the necessary crop clearance," Bossuyt told us. So the solution was to explore the possibility of driving the front wheels hydraulically.

Bossuyt Brothers Farms produces cereal and oil seed crops on 3,800 acres of clay/gumbo soil near Oak Bluff, Manitoba, in Canada's Red River Valley. "The wet weather soil conditions are challenging, particularly so for the commercially built spraying equipment currently available from a variety of manufacturers," said Garett Aubin, a technical support and system designer at HyPower, a full-line hydraulics distributor in Winnipeg.

HyPower proposed a hydraulic front-wheel-assist system consisting of hydraulic two-speed wheel motors powered by an Eaton 72400 hydrostatic pump that works through a positraction flow divider. The system also uses a 26000 Series gear pump to operate the spray pump, booms, and other auxiliary equipment. Everything in the system is programmed and controlled using an Eaton EFX 1624 electronic controller.

Aubin told us:

One of the challenges we faced was providing consistent and accurate flow to the front wheel motors even when the automatic transmission on the truck’s powertrain downshifts in high torque situations. Because the hydrostatic pump is driven directly from the truck’s engine, we have to deal with varying pump input speeds, as well as changing flow requirements based on ground speed and separate motor displacements depending on whether [you are] in high- or low-speed mode. This is where the F(x) controller really proved itself.

Given the concerns about weight and sinking into the mud, I was surprised with the relatively thin tires. Being in the mining industry for a number of years, the first thing that was done when needing "high flotation" was to increase the width of the tracks in that case. I wonder why a wider tire wasn't implemented here - or is that a farming requirement due to the width of the furrows?

Chuck, the silo story is another impressive story about hydraulics used on the farm. Are these issolated instances of inventive solutions -- or, do some of these solutions get commercialized. I would guess the need goes beyond these individual instances.

A spray rig needs to be able to make extremely tight turns at the end of the field. Any normal steering axle that is also driven would be limited by the angle of the wheels because of the universal joints. Some 4 wheel drive tractors use a right angle drive at the top of the steering kingpin through a hollow kingpin down to the wheel. Problem for an application like this with extremely low production would be that the cost of machining and fabrication of the special gears and such would be prohibitive.

The rear wheels can be driven by a set of gears, or belts, or chains without a problem, but the ability to turn makes the front axle more difficult.

Don't know if you have ever spent any time on any farm equiptment, but it is normal that ag equiptment is able to have a turn radius that is little longer than the length of the vehicle. A normal 4 wheel drive truck has a turning radius larger than a comparable 2 wheel drive truck. And most 4 wheel drive axles, when engaged, require an even larger turn radius.

Consider that a field will have rows spaced 30"(or 24"). The wheels may be spaced at 120" to go down the center of the rows. That puts 4(or 5) rows under the tractor. There will be 3 rows outboard on each side. So I get to the end of the row and pick up the implement at the end of the row and as soon as it is clear of the crop I do a hard turn to clear the fence at the edge of the field (and I don't allow any extra rom because if I make the turn around area 4 foot bigger I lose a couple acres at each end of the field) and then I make a sharp turn into the sixth row over and head to the other end of the field. If I have to wrestle with a vehicle with a large turn radius I will waste a lot of time trying to get out of the currrent row and into the next. With 3500 acres to work I don't have a lot of time to spend maneuvering, as getting the current spray on the field may be a time sensitive operation.

The picture shows "crop clearance" for the rear wheels, but the article states "The normal transmission output is used to drive the rear wheels." I'm used to seeing a traditional differential rear end, but I obviously dont' see a "pumpkin" hanging down low.

Did they install some sort of bevel gear adapters on the end of the normal differential, with an equivalent set down on the wheel centers?

I agree it's impressive, Rob. The ag industry is known for innovative use of hydraulics and this is a perfect example. A few years ago (okay, maybe it was 25 years ago), I did a story for Design News about a farmer who developed an electrohyadulic actuation system to tip over a silo, lay it on its side, and lift it onto a flat bed trailer.

This is quite an impressive makeover. I would guess there are plenty of situations where this electrohydraulic vehicle would solve problems on farms. I wonder if these folks are planning to commercialize their vehicle.

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